This invention relates to a device for supplying a more volatile fuel to an internal combustion engine in addition to its main, usually less volatile fuel supply.
It is well known to supply enrichment fuel to an internal combustion engine under certain conditions. For example, enrichment fuel may be provided so as to assist in starting and/or for cold running warmup. Generally the enrichment fuel is supplied to the engine only during cold startup, and the supply of enrichment fuel is discontinued only after sufficient warming of the engine has occurred.
Although systems have been available for supplying enrichment fuel, the procedures involving their use are typically burdensome. On startup, the enrichment fuel is made available to and usually primed into the engine, frequently means are provided to continue the supply of enrichment fuel during warming, and finally a procedure for terminating the use of the enrichment fuel after warming is usually necessary.
The problems associated with cold starting are particularly troublesome in the case of the two cycle engine which may be operated with a lower quality of fuel such as alcohol or kerosene, which have a lower volatility than gasoline. There are advantages to operating with a lower volatility fuel, including lower cost. Often, lack of availability of higher volatility fuels necessitates the use of lower volatility fuels such as kerosene.
Some engines have separate valves and a priming pump with a stepwise procedure for operating each one. Further, once the engine is running and while the boat is moving, it may be difficult to perform procedures to shut off the enrichment fuel.
In addition, when a supply of enrichment fuel is present, the tank from which it is withdrawn needs to be vented to displace the withdrawn enrichment fuel with air. Venting the tank open could cause spills if the tank is filled. A separate vent valve would entail another operating step in the startup and the shut-down procedure.
In two cycle engines the main fuel supply typically finds its way to the combustion chamber through the crankcase and then through scavenging ports on the sides of the cylinder walls. On cold startup, the fuel supplied in this way to the engine may significantly condense in the crankcase preventing its effectively reaching the combustion chamber. This is particularly true during the times of low fuel flow, as when the engine is idling and when using low quality low volatility fuels.
Systems which provide to an engine the fuel needed for operation are typically referred to as charge forming devices. In the two-cycle engine, provision may be made for an idling circuit which involves the application a small amount of the main fuel directly to a point near the main combustion chamber of the engine rather than through the crankcase during idling. Any enrichment fuel system should be formed integral with and become a cooperative member of the engine's charge forming device.
Some systems have incorporated pumping devices into the charge forming system of an engine for supplying only a finite amount of enrichment fuel. These pumping devices are generally "one shot" types of devices that only provide an initial squirt of enrichment fuel before starting, and then no more. Other systems merely make a supply of enrichment fuel available, in which case the user may be able to marshal an adequate supply of enrichment fuel in the combustion chamber only after several successive cranking operations. Neither of these devices are satisfactory.
The provision of an enrichment fuel supply device in an engine charging system involving minimum steps for its operation, and which would provide the advantages of both a flowing supply and "one shot" priming would yield new and significant advantages over the prior art.